The Pica 6055 Refill Lead is a special hardness, rated at 10H, that is so durable it can accurately mark on material such as brick, stone, concrete and steel. When you’re thinking about incorporating tougher material into your woodworking project, this is the lead you need to get the job done right. The 6055 rectangular leads measure at a 2x5mm profile and 150mm in length. Each 6055 pack contains 12 leads inside a sturdy, reusable plastic case. Pica BIG DRY Refill-set Stonemason 10H